Does anyone know the mod with the green ghost cat that eats you and puts you in his butt.

Fight spirits to survive in a haunted house! ... Or don't. · By
If the mods have a resources folder you should be able to just add them into the one in the game, but if not you just add the various things from the mod into the correct places.
If it's an enemy mod you put the mod's json into the enemy json folder, you put their sprites folder into the sprites folder - not the individual sprites, just the folder with the sprites in it - and you put their sounds in the sound folder.
I believe if it's a player character mod you do generally the same thing - json into the player json, etc... - but you also have to replace everything, so replacing japes' current jason and sprites with the new character's stuff.
If you want to also do things like effect how likely an enemy is to spawn in certain zones there is also a Modding Resources folder that has a guide in there.
Just so everyone knows, there's a collection of mods here. G&J - Mod Gallery
im not sure but i think it got hacked... it were shutted down at one point, but once it came back some of mods became "unavaidable" and now it doesnt seem to be updated, it is up to this point but the mods were not restored, and no new mods have apeard in the gallery since the hack thingie (from moment i post this comment)
As far as I know, it hasn't been hacked at least.
It should be temporarily closed by the website administrators (for some reason).
The reason why some mods become "unavailable" may be due to requests from their authors.
As for the lack of mod updates... I think it's just because no one is making new mods anymore haha.